<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
   <style>
     .box {
        width: 100px;
        height: 100px;
        background: orange;
    }
   </style>
</head>
<body>
    
    <div id="app">
        <!-- v-bind  动态绑定属性  -->
        <!-- 可以简写 v-bind:  ===  : -->
        <div :class="className" >

        </div>
    </div>

    <script src="https://cdn.jsdelivr.net/npm/vue@2/dist/vue.js"></script>
    <script>

        new Vue({
            // 元素
            el: "#app",
            // 定义的数据(状态)
            data: {
                className: 'box'
            }
        })
    </script>
</body>
</html>